This invention relates to polymer compositions, particularly ethylene/octene copolymer-containing compositions, suitable for use as semi-conductive and insulating compositions such as in electrical cables. More particularly, the present invention relates to semi-conductive and insulating compositions including an ethylene/octene copolymer and another polymer, such as an ethylene/vinyl acetate copolymer. The polymeric composition may also contain such additives as carbon black, antioxidants and curatives, depending on the final use of the polymeric composition.
Ethylene/vinyl acetate is known as a useful polymer in formulating polymeric compositions, particularly for use in electrical conductors such as power cables and wire. For example, U.S. Pat. No. 4,612,139 to Kawasaki et al. discloses semi-conducting compositions containing between 59 and 84% by weight of an ethylene/vinyl acetate copolymer. The balance of the compositions disclosed therein includes carbon black, antioxidants and curatives. Similarly, U.S. Pat. No. 4,305,849 also to Kawasaki et al. discloses insulating compositions containing either polyethylene or ethylene/vinyl acetate as the polymer component. The compositions further include polyethylene glycol, antioxidants and curatives.
The use of other polyolefin polymers to form polymer compositions is also known. For example, U.S. Pat. No. 4,812,505 to Topcik discloses heat and water tree resistant compositions containing copolymers of ethylene and an .alpha.-olefin. Examples of the polymers are polyethylene, ethylene/1-butene, ethylene/propylene/1,4-hexadiene, ethylene/propylene/ethylidene and ethylene/propylene.
However, none of the references discloses the incorporation of an ethylene/octene copolymer and a second polymer into a polymeric formulation, or the specific combination of both an ethylene/vinyl acetate copolymer and an ethylene/octene copolymer into an insulating or semi-conductive polymeric composition.
Other patent references disclose the use of octene monomers, such as 1-octene, in polymer compositions. For example, U.S. Pat. No. 5,278,272 discloses substantially linear polymers incorporating ethylenically unsaturated monomers such as 1-octene into the polymer compositions. U.S. Pat. No. 4,997,713 discloses polymeric formulations for electrical cables, wherein the polymeric formulation comprises (1) an ethylene/.alpha.-olefin copolymer and (2) an ethylene homopolymer, an ethylene/alkyl acrylate copolymer, an ethylene/alkyl acrylate/acrylic acid terpolymer, or a mixture thereof.
U.S. Pat. No. 4,851,463 also discloses the possible inclusion of ethylene/1-octene into a fire retardant polymeric composition, wherein the fire retardant polymeric composition includes an ethylene copolymer, a C.sub.2 -C.sub.6 .alpha.-olefin polymer, and other additives. However, the patent does not disclose a polymeric composition specifically comprising an ethylene/octene copolymer.